The first item raises a question: is there some use case where one wants to run tests against *different* django version? To me it seems one wouldn't want to do this, the tests are tied to specific django version.

Reopening the sys.path.insert call makes the test setup differ from standard installation procedures. We've for a long time tried hard to move away from modifying the sys.path.

As a background, by mangling the sys.path we risk missing import errors that happen when Django is installed with tools like pip. Instead we should promote the use of pip install -e path/to/django when developing Django.